Test Vitamin D levels in pregnant women say researchers

Australian clinical researchers have identified widespread Vitamin D deficiency in pregnant women as well as a very strong association between low Vitamin D levels and gestational diabetes.

Media Release: 04 April 2011

Australian clinical researchers have identified widespread Vitamin D deficiency in pregnant women as well as a very strong association between low Vitamin D levels and gestational diabetes.

In a retrospective study of 147 women from a gestational diabetes clinic at Westmead Hospital, 41% were shown to be Vitamin D deficient.

Not only that, the lower the Vitamin D, the worse the women’s blood sugar control – measured through a test known as the ‘HbA1c’, which averages blood sugar levels over the preceding two months.

Vitamin D is produced in skin after exposure to sunlight. Fatty fish, eggs and meat are rich in the vitamin and some products such as milk and margarine are fortified. Many Australians are Vitamin D deficient.

Low levels in pregnancy are worrying, irrespective of whether or not a woman has diabetes, because Vitamin D deficiency can have serious consequences on the future bone health of the child. Because of this, the researchers recommend testing of all pregnant women in Australia for Vitamin D.

Dr Sue Lynn Lau and Dr Jenny Gunton, from Sydney’s Garvan Institute of Medical Research, with Dr Neil Athayde and Professor Wah Cheung from Westmead hospital, have published their findings in the Medical Journal of Australia.

“Our findings appear to suggest that boosting Vitamin D in pregnant women may improve glucose tolerance, and that in turn could potentially reduce the complications of diabetes in pregnancy like caesarian sections, babies that are born too big and babies that have low blood sugars,” said Dr Gunton.

“Boosting Vitamin D would definitely contribute to a decrease in the rate of rickets and bone complications in the babies. Low Vitamin D levels in mothers are known to correspond with low Vitamin D levels in their babies – and we’ve been seeing a resurgence of rickets in Australian children because they’re Vitamin D deficient.”

The doctors decided to do the audit at their clinical practice, after noticing that a large percentage of women appeared to be Vitamin D deficient.

“We had routinely been checking Vitamin D levels of women with gestational diabetes at the same time as we did their other diabetes tests,” said Lau, who studied vitamin D and diabetes for her PhD.

“We decided to go through all our records systematically and document what percentage of women were deficient, and whether the rates were higher in any particular group than in others.”

“While we were doing that, and just purely out of interest, we looked to see whether there was any correlation between the HbA1c, a test of glycaemic control, and the Vitamin D level. It showed up as highly significant.”

“Recognising that there could have been many confounders causing a correlation on a simple comparison of two things, we went back and took into account lots of other factors, including ethnicity and age and body mass index.”

“When we did the more complex statistical analysis, we found there was still a significant relationship between the level of Vitamin D deficiency and the control of the diabetes in pregnancy.”

“I think it’s premature to say the association is causative because there may be separate factors that lead to both Vitamin D deficiency and poor glycaemic control, although we did try to adjust for all those possible factors.”

Gunton believes that the results of this association study are compelling enough to demonstrate the need for intervention data, as well as a proper placebo controlled trial.

“Regardless, a 41% deficiency rate in women with diabetes in pregnancy is unacceptable,” she said.

“We suggest that all women with diabetes in pregnancy should have their vitamin D levels checked, and if they are low, they should be treated.”